Methods and apparatus for measuring an electrical parameter (dielectric constant, capacitance, dissipation factor etc.) of a material are described in the following publications, which are incorporated by reference herein: "ASTM D150-81: Standard Test Methods for A-C LOSS CHARACTERISTICS AND PERMITTIVITY (DIELECTRIC CONSTANT) OF SOLID ELECTRICAL INSULATING MATERIALS"; Hewlett Packard Application Note 339-13, "MEASURING THE DIELECTRIC CONSTANT OF SOLID MATERIALS:--HP 4194A Impedance/Gain--Phase Analyzer"; and Gen Rad Impedance Measurement APPLICATION NOTE 11, "Dielectric Loss and Permittivity Measurements with Gen Rad Precision Capacitance Bridges."
In prior art electrode systems (ESs), a material whose dielectric constant, for example, is to be measured is typically required to be in the form of a flat disk or plate having parallel surfaces. The ES therefore assumes the form of a parallel plate capacitor; that is, the ES comprises two planar electrodes which must be nearly perfectly parallel to one another. These limitations on the shape of the sample and on the shape and orientation of the electrodes present several practical problems, including maintaining the parallelism of the electrodes during normal use and after replacement of the electrodes, and accurately calibrating the measurement system. Moreover, prior art ESs are generally limited to either horizontal or vertical use, but not both. This later limitation is due to the fact that the pressure exerted on the sample being investigated significantly affects the measurements. Thus, prior art ESs designed for horizontal use cannot make accurate measurements when oriented vertically, and vice versa.
Accordingly, it is an object of the present invention to provide an ES which is convenient to use, comprises means for adjusting the parallelism of its electrodes, and can make accurate and reliable measurements in either a horizontal or vertical position. The present invention achieves these objectives.